Cookie count exceeded in edit mode

Description

Steps to Reproduce:
1. Clear all your cookies.
2. Navigate to a page that has a block inserted in a content area.
3. Open "All Properties" view. 
4. Open the context menu of the block in the content area.
5. Click "Edit" to edit the block.
6. Inspect cookies.
7. You should have a new cookie name like "uniqName_60_1SaveSelectedCookie" with a value of "root%2F<ContentID?><A guid/Working id?> 
8. If you do steps 2-5 again for the same block, a new cookie is generated.

Expected:
Edit mode should not be affected (The cookies should be deleted).

Actual:
Edit mode stops working (requests failed with cookie limit reached).